Suppose you have an array of hashes like this:
```ruby
arr = [{a: 1, b: 2}, {c: 3, d: 4}, {e: 5, f: 6}]
```
You can extract the values corresponding to a given key like this:
```ruby
arr.map { |h| h[:a] }
# => [1, nil, nil]
```
```ruby
arr.map { |h| h[:b] }
# => [2, nil, nil]
```
```ruby
arr.map { |h| h[:c] }
# => [nil, 3, nil]
```
```ruby
arr.map { |h| h[:d] }
# => [nil, 4, nil]
```
```ruby
arr.map { |h| h[:e] }
# => [nil, nil, 5]
```
```ruby
arr.map { |h| h[:f] }
# => [nil, nil, 6]
```
If you want to get all the values for all the keys, you can use `#values`:
```ruby
arr.map { |h| h.values }
# => [[1, 2], [3, 4], [5, 6]]
```

end_index # => the end of index
There are 3 ways:
arr[0...end]
arr[0, end]
arr.first end